A stack of paper sheets can be bound together at an edge by applying a thermally flowable adhesive to the edge and permitting it to penetrate slightly into the stack of pages and harden. For example, Minami U.S. Pat. No. 3,866,568 discloses a machine for binding a stack of sheets by causing the lower edge of the stack to travel past the upper surface of a drum rotating in a tank of heated adhesive so that adhesive is applied to the lower edge of the stack; immediately before the front edge of the stack reaches the drum, the drum is temporarily lowered out of adhesive-applying position, to keep excess adhesive from the front edge of the stack of sheets.